Here’s an excerpt from my prior posts on the subject 
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A remaining number indicates a gap between what was recommended and what you have completed for the day. It doesn’t mean you have to close that gap.
The deficit/surplus doesn’t carry over to the next day. Although calculated to show pts below/above Noon position on the Training Pacer, it’s not an exact number you must heed.
It’s the value to return to Noon position (neutral) vs dipping toward red (Falling Behind) or riding more and getting Ahead of Plan. Your main goal is to keep the needle in the 11am-1pm position to attain/maintain your currently selected IR (improvement rate). That position may vary over the week (or week to week) as your schedule permits.
The Pacer Needle reflects a moving weighted average over a rolling 7 days. This is a significant difference between Xert and platforms based on targeted TSS tables. There is a flexible ebb and flow nature to Xert. You can also change the flow rate to accommodate changes in your schedule and ability to train more or less hours week to week.
Longer version 
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